This is a randomized clinical trial aimed at determining the efficacy and safety of blade implant supported bridges relative to equivalent non-implant supported cantilever bridges, and at developing a clearer understanding of implant acceptability, disease activity and the mechanism of failure. Its aim is also to develop and refine methodology for randomized clinical trials in dentistry. Thirty-four patients, both male and female, between the ages of 21 and 60, homogeneous in that they are edentulous in the maxilla and exhibit bilateral edentulous mandibular sites posterior to the first bicuspid, have been selected and treated with complete maxillary dentures opposing bilateral four-unit fixed bridges. Blade implants act as distal abutments for one-half of these fixed bridges, which are being compared to equivalent contralateral distally unsupported cantilever fixed bridges. These fixed bridges have been designed to be removable for mobility evaluation of abutment teeth and implants by periodontometry. Angle standardized radiography, gingival health and pocket depth are additional evaluation criteria being used. Post-treatment follow-up is collected at 4, 8, and 12 weeks and every three months thereafter for five years for each patient. Statistical analysis is to be undertaken for the hierarchical record system of clinical information. More specifically, the data structure is organized according to tooth (4 abutment teeth and implant) within visit, within treatment phase and within patient. The data are obtained at each visit during the respective treatment phases as follows: initial, pre-prosthetic, immediate post-prosthetic, and periodic follow-up evaluation over three years. Statistical analysis will be concerned with the extents of change of the clinical measurements for abutment teeth on the implant vs. cantilever side. Also, some attention is to be given to adjustment for baseline status at the initial or immediate post-prosthetic visit. Finally, life table methods are to be used for the analysis of survival data.